Aluminum Isopropoxide Research Articles

Synthesis and Characterization of Schiff Bases Derivatives of Heterotrimetallic [Al(III); Sn(II); Ti(IV)]-µ-oxo-isopropoxide-µ-oxon-propoxide [SnO2TiAl(OPri)2(OPrn)3

Tin diacetate and aluminium isopropoxide in equimolar proportion in xylene affords the complex [(OAc)SnOAl(OPr i ) 2 ] which on reaction with Ti(OPr n ) 4 in 1:1 molar ratio yielded a new organoheterotrimetallic-μ-oxoisopropoxide-μ-oxon-propoxide [SnO 2 TiAl(OPr i ) 2 (OPr n ) 3 ] with continuous liberation of isopropyl acetate and propyl acetate formed during the course of reaction. The preparation of Schiff base complexes of the compound [SnO 2 TiAl(OPr i ) 2 (OPr n ) 3 ] was carried out in refluxing benzene by the reaction of µ-oxomixedpropoxide compound in different molar ratios (1:1 and 1:2) with Schiff bases (1-(2-Pyridyl) ethanonehydrazine carboxamide (HSB 1 ) and 1-Furanyl) ethanonehydrazin carboxamide (HSB 2 ). The complexes were characterized by spectral analysis (IR, 1 H, 13 C, 119 Sn, 27 Al NMR and mass spectra). The spectral studies confirmed that the proposed framework of the new organoheterotrimetallic complexes and indicated a tetrahedral geometry around the central metal atom.

UZM-8 Zeolite Synthesized from Solid Aluminosilicate Gel and Its Catalytic Performance

Instead of conventional aluminum isopropoxide and silica sources, commercially available solid aluminosilicate gel with SiO2/Al2O3 = 25 was selected to synthesize UZM-8 zeolite with diethyl-dimethy...

Post-synthetic Mechanochemical Incorporation of Al-Species into the Framework of Porous Materials: Toward More Sustainable Redox Chemistries

The mechanochemical incorporation of catalytically active Al species in low loadings was successfully accomplished into the framework of mesoporous silica (SBA-15 and MCM-41) materials using a simple wet milling approach (with aluminum isopropoxide as source of aluminum) and a dry milling approach (using low quantities of Al-containing MOF materials). Characterization data pointed to the successful incorporation of Al species (typically with loadings of ca. 0.2–0.4 wt %) that were mostly tetrahedrically coordinated. Despite such extremely low loadings, the isolated aluminum oxide species exhibited promising activities and stability in selective mild oxidations under various conditions (microwave irradiation and mechanochemistry), including the selective oxidation of benzyl alcohol to benzaldehyde, isoeugenol to vanillin, and diphenyl sulfide to diphenyl sulfoxide, as compared to similarly synthesized impregnated catalysts.

Comparison study on molybdena-titania supported on TUD-1 and TUD-C synthesized via sol-gel templating method: Properties and catalytic performance in olefins epoxidation

A direct comparison between nanostructured Technische Universiteit Delft-1 (TUD-1) and Technische Universiteit Delft-Crystalline (TUD-C) as catalyst supports for molybdenum doped titania catalysts was carried out. The characterizations results showed that TUD-1 is a mesoporous amorphous silicate material with high surface area and porosity. Meanwhile, TUD-C is an ordered mesoporous crystalline aluminosilicate matters featured high acidity. In fact, TUD-C was obtained from the modification of TUD-1 with the addition of aluminium isopropoxide as the zeolite precursor. The catalytic testing demonstrated TUD-1 supported 1 mol% molybdena doped titania was inactive for epoxidation of 1,2-epoxyoctane and showed moderate activity (18%–21% conversion yield) and selectivity (approximately 70%) in epoxidation reaction of 1,2-epoxycyclohexane (0.51 mmol) and styrene oxide (1.25 mmol). Meanwhile, TUD-C supported 1 mol% molybdena doped titania achieved remarkably higher conversion yield for 1,2-epoxyoctane (2.7 mmol), 1,2-epoxycyclohexane (4.8 mmol) and styrene oxide (6.2 mmol) respectively with 100% selectivity towards all 3 analytes under ambient condition with constant stirring. The results strongly indicated that high Brønsted and Lewis acidic sites existed within the TUD-C framework is the key factor for the exceptional oxidative capabilities for molybdena-titania catalysts.

One-Pot Synthesis and Formation Mechanism of Hollow ZSM-5.

Coffin-shaped hollow ZSM-5 zeolite (HZZ) particles with shell thickness of about 200 nm and hollow diameter of approximately 1.5 μm were synthesized in one pot by using tetrapropylammonium bromide (TPABr), aluminum triisopropoxide Al[OCH(CH3 )2 ]3 and tetraethoxysilane (TEOS) as the structure-directing agent (SDA), aluminum and silica source, respectively. The appropriate molar ratios of TPABr/SiO2 and Si/Al as well as suitable crystallization temperature are the key factors for the formation of HZZ. The formation of the HZZ can be attributed to the existence of intrinsic density variation inside the initial amorphous aggregates and the Al zoning in the outer surface of the ZSM-5 particles. Amorphous silica with low crystallinity formed at early stages and low Al concentration, which has been subsequently dissolved and recrystallized on the ZSM-5 particle surface through Ostwald ripening, leading to the formation of HZZ. This approach, which uses a high concentration of SDA, will provide new possibilities and insight into the prospective fabrication of hollow zeolites.

Effect of vitamin C template on morphology and structure of alumina: emerging application in enantiomer separation

Mesoporous nano-aluminas were prepared using aluminium isopropoxide, vitamin C (VC as a chiral template and a co-structural directing agent with molar ratios of 50:50 and 90:10) and water. These compositions when dried at 120 °C and calcined at 250, 350 and 500 °C for 8 h under air atmosphere transformed to boehmite and γ-alumina depending on the concentration of VC. The influence of vitamin C and its degradation products on the morphology and texture of alumina was investigated by the means of XRD, FT-IR, SEM, EDX, TEM, TGA, DSC, BET and N2 adsorption–desorption isotherm. Mesoporous aluminas possess excellent characteristics such as large surface area (ca. 394 m2/g), 0.4 cm3/g pore volume and narrow pore size distributions that can be synthesized through a facile and green procedure. In addition, the enantiomers of propranolol hydrochloride were successfully resolved from its racemate using Al50VC50T350 (AlMolar ratio of the Aluminium isopropoxide, VCMolar ratio of the Vitamin C,TTemperature) (Rs = 2.5) as chiral stationary phase. The synthesis of chiral stationary phase was accomplished in a green, facile and inexpensive procedure that is of paramount importance in food and pharmaceutical industries.

Catalytic activation of all-silica COK-14 zeolite through alumination and particle size reduction using wet ball milling

The precursor of all-silica COK-14 zeolite (OKO topology) with interrupted framework was subjected to wet ball milling in the presence of aluminum isopropoxide. Alumination and particle size reduction of the zeolite crystals was combined in this way. Wet ball milling resulted in fragmentation of the platelet-shape COK-14 crystals while preserving crystallinity. 27Al NMR spectroscopy of the fully condensed COK-14 zeolite, obtained by calcination of milled -COK-14 precursor, confirmed the incorporation of tetrahedrally coordinated Al atoms in the framework. The creation of Brønsted acid sites was confirmed by pyridine adsorption. Loaded with platinum, the sample showed ideal bifunctional catalytic behavior in hydroisomerization and hydrocracking of n-decane model alkane compound. Aluminum incorporation by milling is an alternative to the atomic layer deposition (ALD) process using trimethylaluminum and to thermal alumination. Wet ball milling in presence of aluminum isopropoxide shows great potential for making siliceous zeolites catalytically active.

Crystallization of AlPO4-11 Aluminophosphate from Various Aluminum Sources

The crystallization of an AlPO4-11 molecular sieve from various aluminum sources, namely, boehmite, pseudoboehmite, and aluminum isopropoxide, has been studied in this work. It has been found that the reactivity of the precursor affects the phase composition of the initial aluminophosphate gels and products of their subsequent crystallization as well as the morphology of the crystals of AlPO4-11 and characteristics of their porous structure.

Dehydrofluorination of 1, 1, 1, 3, 3-pentafluoropropane over C-AlF3 composite catalysts: Improved catalyst stability by the presence of pre-deposited carbon

A series of C-AlF3 composite catalysts were prepared using a sol-gel method and different aluminum precursors (i.e. aluminum isopropoxide (Al(OiPr)3) and aluminum diacetate hydroxide (C4H7AlO5)). These catalysts were very active in gas-phase dehydrofluorination of 1, 1, 1, 3, 3-pentafluoropane. For example, a catalyst calcined at 400 °C with aluminum isopropoxide as the precursor (denoted as C-AlF3-AIP-400) gave a reaction rate of 8.30 μmol s−1 gcat-1 and a selectivity to 1, 3, 3, 3-tetrafluoropropene (HFO-1234ze) of above 99% at 340 °C. More importantly, the C-AlF3 catalysts showed excellent stability during 100 h reaction, while the pure AlF3 catalyst suffered severe deactivation owing to the coke deposition on the surface. In contrast, pre-deposited carbonaceous species formed in the catalyst due to the incomplete decomposition of organic precursors during the preparation procedure, which blocked strong acidic sites in the AlF3 and thus maintained the catalyst stability. Therefore, these findings provide useful information on the development of efficient catalyst for this reaction, particularly on the maintainance of catalyst stability.

Facile electrodeposition of superhydrophobic aluminum stearate thin films on copper substrates for active corrosion protection

A facile aluminum based superhydrophobic thin films were electrodeposited by mixing aluminum isopropoxide (AlOx) with stearic acid (SA) onto the copper substrates via one-step method. The energy dispersive X-ray spectroscopy (EDS) attenuated total-reflectance Fourier Transmission infrared spectroscopy (ATR-FTIR) were used to confirm the presence of Al, C, and O as well as COOAl and CH bonds in the thin film. The water-roll off properties were analyzed by measuring the contact angle to study the superhydrophobic nature of fabricated films. Results show that superhydrophobicity with the water contact angle of 161 ± 1° and the contact angle hysteresis of 2 ± 1° were obtained with respect to the AlOx/SA molar ratio of 0.33. The morphology of the fabricated thin films consisted of uniform porous structures with surface roughness (rms) of 3 μm on the copper substrate. The addition of stearic acid plays an important role for the superhydrophobic property. Furthermore, the thin films and their anticorrosion behavior were investigated using 3.5 wt% corrosive aqueous NaCl electrolyte solution. The polarization resistance of the thin film is found to be 962 kΩ·cm2 as characterized by Tafel. Similarly, impedance value of 10 MΩ·cm2 was obtained from Electrochemical Impedance Spectroscopy (EIS). A simple fabrication of water-repellent superhydrophobic aluminum-based coating endues extremely high active in corrosion protection.

Sintering Ce-TZP/alumina composites using aluminum isopropoxide as a precursor

A homogeneous 12Ce-TZP/30 vol% Al2O3 composite material has been manufactured by pressureless-sintering in air green compacts of a powder mixture incorporating aluminum isopropoxide as an organic precursor. Densification of the composite material occurs by grain boundary diffusion and is controlled by the diffusion of Ce cations.

2-Ethyl-9,10-anthraquinone assisted sol–gel synthesis of Pd/γ-Al2O3 nanorods with enhanced catalytic performance in 2-ethyl-9,10-anthraquinone hydrogenation

A series of nanorod-like porous Pd/γ-Al2O3 catalysts with controllable textural properties and enhanced catalytic performance in 2-ethyl-9,10-anthraquinone (eAQ) hydrogenation for H2O2 preparation were successfully prepared via a facile sol–gel method using aluminum isopropoxide as aluminum precursor and eAQ as structure directing agent, sequential calcination and impregnation process with Na2PdCl4 solution. The physicochemical properties of the catalysts obtained with different addition amounts of eAQ were comparatively characterized by XRD, TG–DSC, BET, TEM, CO-TPR, H2-TPR and H2–O2 titration. The results show that addition of eAQ can not only effectively control the textural properties (surface area, pore volume and average pore size) of the catalysts, but also lower their reduction temperature of active metal. Importantly, the catalyst obtained with an addition amount of 4 wt% eAQ shows the highest hydrogenation efficiency of 10.28 g·L−1, which is 37.3% higher than 7.49 g·L−1 of the catalyst obtained without eAQ.

Ligand-Dependent Colloidal Stability Controls the Growth of Aluminum Nanocrystals.

The precise size- and shape-controlled synthesis of monodisperse Al nanocrystals remains an open challenge, limiting their utility for numerous applications that would take advantage of their size and shape-dependent optical properties. Here we pursue a molecular-level understanding of the formation of Al nanocrystals by titanium(IV) isopropoxide-catalyzed decomposition of AlH3 in Lewis base solvents. As determined by electron paramagnetic resonance spectroscopy of intermediates, the reaction begins with the formation of Ti3+-AlH3 complexes. Proton nuclear magnetic resonance spectroscopy indicates isopropoxy ligands are removed from Ti by Al, producing aluminum(III) isopropoxide and low-valent Ti3+ catalysts. These Ti3+ species catalyze elimination of H2 from AlH3 inducing the polymerization of AlH3 into colloidally unstable low-valent aluminum hydride clusters. These clusters coalesce and grow while expelling H2 to form colloidally stable Al nanocrystals. The colloidal stability of the Al nanocrystals and their size is determined by the molecular structure and density of coordinating atoms in the reaction, which is controlled by choice of solvent composition.

SYNTHESIS OF MESOPOROUS γ-ALUMINA AND ITS CATALYTIC PERFORMANCE IN DICHLOROPROPANOL CYCLIZATION

This paper discusses the synthesis and resulting catalytic performance of mesoporous alumina using aluminum isopropoxide as the aluminum source, and synthesized organosiloxane KH560-540 as template. The effects of the hydrothermal conditions, as well as the amount of templating agent at pH values of 5-9 on the structure of the synthesized mesoporous alumina were investigated by nitrogen adsorption-desorption methods, XRD and electron microscopy. Alumina from a rod-like scaffold structure was obtained, and the specific surface area was as high as 508 m2 g-1. Also, the coordination state of aluminum before and after calcination was analyzed by 27Al-NMR spectroscopy. The role of the templating agent in the synthesis process was determined. The synthesis mechanism of mesoporous alumina prepared by a KH560-540 template was also proposed. The acidity of samples that were synthesized by different templating agents were compared to NH3-TPD, and the content of Si in each sample was tested by ICP-OES, the results show that the silicon content has little effect on the acidity of the sample. Finally, we used the synthesized mesoporous alumina to catalyze the cyclization of dichloropropanol to epichlorohydrin, which showed excellent catalytic performance:dichlorohydrin conversion is up to 96% and epichlorohydrin yield of nearly 92%.

Amorphous Alumina Films Efficiently Protect Ti6242S against Oxidation and Allow Operation above 600 °C

The protection of the titanium based Ti6242S alloy against oxidation at moderate temperature is investigated, through the application on its surface of a 300 nm thick, amorphous alumina film. The latter is processed by metalorganic chemical vapor deposition at 500 °C from dimethyl aluminum isopropoxide. Upon oxidation at 600 °C for 5000 h, an interfacial zone is created between the alloy and the external protective layer, composed of unaffected alumina. In these conditions, the mass gain per unit area is eight times lower than that of the bare alloy, while the hardness of the alloy remains unaffected, revealing negligible oxygen ingress attributed to the efficiency of the protective coating. Finally, alumina coated samples show negligible mass change after 80 one-hour thermal cycles between 50 °C and 600 °C, showing excellent coating adherence on the Ti alloy.

Atomic Layer Deposition of Al2O3 Using Aluminum Triisopropoxide (ATIP): A Combined Experimental and Theoretical Study

The aluminum precursor plays a crucial role in the Al2O3 ALD process. To date, trimethylaluminum (TMA) is one of the most widely used precursors in experimental and theoretical studies. However, its application at industrial scale can pose safety risks since it is pyrophoric and extremely reactive with water. Aluminum alkoxides offer a promising alternative, but have received far less attention. A combined theoretical and experimental investigation is carried out on the Al2O3 ALD process using aluminum triisopropoxide (ATIP) as a prototypical example of Al-alkoxide precursors. The experimental results pointed out that the thermal ALD process using ATIP and water has a maximal growth per cycle (GPC) of 1.8 A/cycle at temperatures of 150 to 175 °C. On the basis of the in situ mass spectrometry analysis and DFT calculations, the formation of the alumina film mainly occurs during the water pulse by ligand exchange reactions between water and adsorbed precursors, while during the ATIP pulse only adsorption of ...

Analysis of TiO2 Atomic Layer Deposition Surface Chemistry and Evidence of Propene Oligomerization Using Surface-Enhanced Raman Spectroscopy.

Atomic layer deposition (ALD) of TiO2 was performed in tandem with in situ surface-enhanced Raman spectroscopy (SERS) to monitor changes in the transient surface species across multiple ALD cycles. A self-assembled monolayer of 3-mercaptopropionic acid was used as a capture agent to ensure that nucleation of the titanium precursor (titanium tetraisopropoxide [TTIP]) occurs. Comparisons between the Raman spectra of the neat precursor and the SER spectra of the first ALD cycle of TiO2 reveal typical ligand exchange chemistry taking place, with self-limiting behavior and intact isopropoxide ligands. However, subsequent cycles show drastically different chemistry, with no isopropoxide ligands remaining at any point during the second and third cycles. Continuous exposure of either TTIP or isopropyl alcohol after the first cycle shows unlimited chemical vapor deposition (CVD)-type growth. Comparisons with alternative precursors (aluminum isopropoxide, titanium tert-butoxide, and titanium propoxide) and DFT calculations reveal that, for the TTIP precursor, isolated TiO2 sites play a role in the dehydration of off-gassing isopropyl alcohol. The resulting propene then undergoes oligomerization into six-carbon olefins before polymerizing into indistinguishable carbon products that accumulate on the surface. The emergence of the dehydration chemistry is expected to be exclusively the result of these isolated TiO2 sites and, as such, is expected to occur on other surfaces where TiO2 ALD is feasible. This work showcases how seemingly innocuous ALD can evolve into a CVD process when the products can participate in various side reactions with newly made surface sites.

Preparation of nanosized NaA zeolite and its surface modification by KH-550

Abstract Nanosized NaA zeolite was successfully synthesized by hydrothermal method using tetraethyl orthosilicate (TEOS) and aluminum isopropoxide (AIP) as the main raw materials. The surface modification of NaA zeolite was carried out by silane coupling agent 3-aminopropyltriethoxysilane (KH-550). The effects of silane coupling agent dosage, reaction temperature, reaction time, hydrolysis time and pH value on grafting rate of NaA zeolite were investigated in detail. The zeolites were characterized by XRD, SEM-EDS, FT-IR and TG-DTA. The results showed that the surface of NaA zeolite was modified successfully by KH-550. The optimal modification conditions obtained were as follows: the dosage of coupling agent in 95 % ethanol – 1.6 %, reaction temperature − 70 °C, reaction time – 2 h, hydrolysis time – 20 min, and pH value – 3.5. Under these conditions, the grafting rate of modified NaA zeolite was 3.95 %.

Sol-gel synthesis and characterization of ZnAl2O4 powders for transparent ceramics

The sol-gel synthesis of ZnAl2O4 ceramic powders from alkoxide and acetate sources of metals, as well as the microstucture and the hardness of the hot-pressed ZnAl2O4 specimens were considered. ZnAl2O4 powders were prepared by the hydrolysis of an alcohol solution of aluminium isopropoxide using an aqueous solution of zinc acetate followed by heat treatment. The thermal evolution of the ZnAl2O4 precursor was investigated. The effect of calcination temperature on the morphology and the specific surface area of ZnAl2O4 powders were also studied. The sintering of the resultant powders to the high transparent ceramic using a hot pressing with 1 wt% ZnF2, as a sintering additive was successfully demonstrated. The in-line transmittance of ZnAl2O4 ceramics (1 mm thickness) achieved 80% in the visible region and 85% at 5 µm; Vickers hardness was 11.6 GPa.

Development of Alumina⁻Mesoporous Organosilica Hybrid Materials for Carbon Dioxide Adsorption at 25 °C.

Two series of alumina (Al2O3)–mesoporous organosilica (Al–MO) hybrid materials were synthesized using the co-condensation method in the presence of Pluronic 123 triblock copolymer. The first series of Al–MO samples was prepared using aluminum nitrate nanahydrate (Al–NN) and aluminum isopropoxide (Al–IP) as alumina precursors, and organosilanes with three different bridging groups, namely tris[3-(trimethoxysilyl)propyl]isocyanurate, 1,4-bis(triethoxysilyl)benzene, and bis(triethoxysilyl)ethane. The second series was obtained using the aforementioned precursors in the presence of an amine-containing 3-aminopropyltriethoxysilane to introduce, also, hanging groups. The Al–IP-derived mesostructures in the first series showed the well-developed porosity and high specific surface area, as compared to the corresponding mesostructures prepared in the second series with 3-aminopropyltriethoxysilane. The materials obtained from Al–NN alumina precursor possessed enlarged mesopores in the range of 3–17 nm, whereas the materials synthesized from Al–IP alumina precursor displayed relatively low pore widths in the range of 5–7 nm. The Al–IP-derived materials showed high CO2 uptakes, due to the enhanced surface area and microporosity in comparison to those observed for the samples of the second series with AP hanging groups. The Al–NN- and Al–IP-derived samples exhibited the CO2 uptakes in the range of 0.73–1.72 and 1.66–2.64 mmol/g at 1 atm pressure whereas, at the same pressure, the Al–NN and Al–IP-derived samples with 3-aminopropyl hanging groups showed the CO2 uptakes in the range of 0.72–1.51 and 1.70–2.33 mmol/g, respectively. These data illustrate that Al–MO hybrid materials are potential adsorbents for large-scale CO2 capture at 25 °C.